Lubricant



June 28, 1932- w WOQDFQRD 1,865,157

I LUBRICANT Filed Oct. 11, 1928 INVENTOR WATSON H. WOODFORD Maj TTORNEYS"Patented June 28, 1932 v UNITED STATES PATENT OFFICE WATSON H.woonronn, or :smnenrom', comvnc'rrcur, ASSIGNOR 'ro nnmerorr ARMS comm,INC.,-A,GORPOBATION or DELAWARE LUBRICANT Application filed October 11,1928. Serial No. 311,941.

7 a This invention relates to lubricants and methods of applyinglubricants to surfaces to be lubricated and will be discussed withspecial reference to the lubrication of bullets.

It is commonly recognized or assumed that lead bullets, foruse in rifledfire arms, require the application of a lubricant for the securing oftheir best performance. In some bullets the lubricant is applied togrooves or cannelures which are placed within the powder case, theprojecting point of the bullet being free from lubricant. Other bulletsare lubricated by the application of lubricant to an exposed cannelure,or the application of lubricant to the entire exposed portion of thebullet. In the past the more popular bullet lubricants have comprisedsuch substances as stearine, petrolatum and ozokerite in mixtures ofvarying compositions. The application of these and similar materialsleaves a greasy surface which renders the bullets and car-- tridgescontaining them somewhat unpleasant to-handle and causes foreignmaterials with a gun barrel.

which the bullets come in contact to readily adhere thereto. It alsomakes them undesirable to be carried in the clothing on account of thesoiling of the clothing with the bullet grease. N i

It is an object of this invention to provide a lubricant which may be.applied to bullets and other articles in such a way as to leave anentirely dry and hard surface, the lubricant however becoming availableas and when it is needed. 7

It is a further object of the invention to construct a cartridgecontaining a lubricated bullet which presents a dry, hard, varnishedsurface, the lubricant however. becoming effective upon the passage ofthe bullet through It is a further object of the invention to effect theproper lubrication of bullets by means of a quantity of lubricant whichis but a small fraction of the quantity heretofore considered to benecessary.

It 'is-a further object of the invention to apply a'lubricant to anarticle to be lubri-- cated bv the use of an emulsionof the lubri- Icant and a volatile fluid.

It is a further object of the invention t secure a lubricant upon anarticle to be lubricated beneath an impervious lacquer film,

- which film is destroyed rendering the lubricant available by thepressure of the lubricated article against a hard surface.

As a part of this invention, it has been discovered that a thin film ofa lubricant, sulficient to secure proper lubrication but far less inquantity than the amount of lubricant ordinarily applied, can be spreadupon the surface of an article, such as a bullet, by preparing anemulsion of a lubricant such as a mineral oil in a volatile fluid suchas ethyl acetate. Upon the evaporation of the fluid the oil remains as athin and more or less contmuous film. The film, however, may not beentirely continuous by, reason of the tendency of the oil to collect indrops during the evaporation of the fluid. As seen under a microscope,the oil droplets in suspension in such a fluid are in constant motion,(the Brownian movement) and the coalescence of different droplets tendsto form drops of increasing size. Advantage is taken of this tendency ofthe oil to collect in drops in another phase vent and that these dropsmay e imprisoned beneath the pyroxylin film which is formed as thesolvent evaporates. A thin film of pyroxylin is formed upon the surfaceof the metal and adheres thereto while a second film is formed over thesurface of the oil drop and adjoins the film adhering to the metal inthe space between the oil drops, as illustrated in the drawing.Lubricating films of varying thickness with varying distribution of theoil throughout the film may be thus secured.

In the drawing:

Figs. 1, 2 and 3are cross sections through various forms of the film.

Figs. 4 and 5 are plan views of photo- 'micrographs of different formsof the film.

If the composition used is such that the solvent evaporates before theBrownian movement has collected the oil into relatively large globules,the fine droplets will be distributed throughout the thickness of thefilm in the manner illustrated in the sectional view, Fig. 2. Theexterior surface of the pyroxylin is in this case comparatively smooth.If the Brownian movement is only partially completed-the oil isdistributed as shown in the sectional view, Fig. 3, a central relativelylarge globule of oil being surrounded by a group of smaller drops, andthe surface of the pyroxylin being somewhat depressed between the drops.

In practice any of the conditions illustrated in Figs. 1-3 may besecured. It has even been found feasible to regulate the number anddistribution of the oil drops by the addition of a known quantity of apulverized, insoluble material such as soapstone, the solid particles ofsoapstone forming nuclei about which the oil drops collect. Thethickness of the film may be varied. say from .0001 inch to .0015 inch.For bullet lubrication a thickness of about .0003 has been founddesirable.

Fig. 4 is a plan view drawn from a photomicrograph of a pyroxvlin filmhaving globules of a mineral oil imprisoned therein. The size of theglobules and the condition of the surface are substantially that shownin Fig. 1. The globules 13 are of generally uniform size, each coveredby an encasing'capsule of pyroxylin, which is continuous with thecoating of the areas 14 separating the capsules.

Fig. 5 is a plan view, also drawn from a photo-micrograph. of the samesurface after it has been subjected to pressure, crushing the capsulesand liberating the oil. Irregular patches of partially lubricant freesurface 15 remain, but the major portion 16 of the surface is welllubricated.

When the lubricating composition is applied to articles such as bulletsby dipping and subsequently allowing the excess composition to drain OK,the oil drops are elongated in the direction of the drainage, and tendto be arrangedin rows which form dis tinct ridges with continuousdepressions beand the oil 12 about 40%- 1,sez s,157

tween them. This condition is illustrated in the plan View, Fig. 6. i

Fig. 7 shows a cartridge comprising a bullet 17 coated with a lubricantcontaining pyroxylin film. The bullet has a dry hard surface, is-cleanto handle, and lint and dirt do not adhere to it. Moreovercolorin'gmatter may be added to the lubricating composition to give the cartridgeor other article an attractive and distinctive appearance. When such acartridge is fired the pressure of the bullet on the wall of the barrelcrushes the lubricant containing capsules and spreads the lubricant overthe entire surface. The lubricant thus becomes avallable at the time itis required, and is inofl'ensive until required.

The quantity of lubricant used is much less than when it is applie inthe usual way. In fact, perfect lubrication is secured with asurprisingly small quantity. Moreover, the absence of an excess oflubricant improves the operation of certain uns, particularly guns ofthe auto loading low back action type. In these guns the gas pressure inchamber and barrel, and the excess lubricant is to a large extent blownback into the action, where it congeals and may accumulate in suchquantities as to cause sluggish operation and misfunctionmg.

I With bullets lubricated according to the present invention little orno lubricant is blown into the action and greatly improved functioningafter extended firing has been secured.

With some lubricants, careful manipulation is necessary in order tosecure imprisoned drops in an adherent film with a dry, lubricant freesurface. Thus for example, stearine yields the best results whenevaporation of the solvent takes place at temperatures be tween about110 and 120i/Fahrenheit. At lower temperatures the stearine isprecipitated in fine particles during the evaporation of the solvent andis distributed throughout the film rather than being encased within thefilm. At somewhat higher temperatures a difierent reaction takes place,which appears to adversely effect the lubricating qualities of thestearine.

The composition of the lubricant emulsion may be greatly varied.Numerous difi'erent oils may be used as well as different pyroxylinsolvents and the amount of oil with any particular pyroxylin solutionmay also be varied. One formula which has given excellent results is asfollows:

Lubricating oil 6.5%, ethyl acetate 7 4.8, dry pyroxylin 13.09, alcohol(in pyroxylin) 5.61.

With this solution the dried film comprises substantially 33% of thelubricating oil and 67% pyroxylin.

While the method and the composition have been discussed application tobullets it will be understood that the invention is not limited to thisparticular field. Both the method of applying chiefly with reference totheir the fluid lubricant by evaporation from a volatile fluid and themethod of protecting a fluid .lubricant by means of a frangible film orcapsule being new with this applicant, the appended claims are to bebroadly construed.

Claims: c

1. A lubricating fluid comprising a fluid lubricant suspended in avolatile fluidl 2. A lubricating fluid comprising a fluid lubricant, a.volatile solvent and material dissolved in said solvent adapted to forman impervious film when the solvent has evaporated therefrom.

3. A lubricating coating comprising an impervious film having drops of afluid lubrieating medium contained within said film.

4. A lubricating coating comprising a pyroxylin film having drops of alubricating fluid contained therein.

5. A lubricating coating comprising a pyroxylin film having drops of amineral oil contained in said film.

6. A lubricating coating comprising an impervious film having drops of alubricatingmedium contained beneath its surface, the surface of the filmbeing raised above such drops whereby said film may be broken and thelubricating medium released by the application of sufiicient pressurethereto.

7. The lubricating fluid comprising a lubricating oil, pyroxyl in andethyl acetate.

8. A lubricating coating for projectiles.

comprising spaced drops of oil, each encased in an impervious, frangiblecapsule.

9. A lubricating coating for projectiles comprising a lacquer filmhaving drops of a fluid lubricant enclosed therein.

10. A lubricating coating for projectiles comprising a pyroxylin filmhaving drops of a mineral oil enclosed therein.

11. A lubricating coating for projectiles comprising a pyroxylin filmcontaining drops of a-fluid lubricant beneath its surface.

12. 'A lubricating coating having a dry non-lubricating frangiblesurface and containing'beneath said dry surface drops of a fluidlubricant which becomes available when said frangible surface is brokenby pressure.

13. A lubricating coating comprising spaced drops of a lubricating fluidcontained within and separated by a solid frangible material adapted tobe broken when subjected to pressure.

WATSON H. WOODFORD.

